Why Elephants Love Nexus

The Project

Chester Zoo is one of the most famous zoos in the world due to its history of exhibit innovations and was often referred to as the “zoo without bars”. It is revered by many as a centre of excellence and a developer of ideas of ways of saving endangered species for the future. Asian elephants have been there since the very start and as the zoo always likes to stay ahead of the times, renovation and modernization are always a regular thing. When it became the elephant house’s turn for rebuilding, it was decided to carry an Asian theme throughout the new structure. Indigenous species of reptiles, birds and tropical fish were added to give the desired affect.

Colin Grist, the zoo’s Aquarium Projects Coordinator, was called in to add his expertise to the project. It had been decided to build a fresh water pond to house some impressive fish synonymous with Asia. These fish had actually been donated to the zoo when small and had grown substantially over time in the zoo’s aquarium. The challenge now was to filter the pond which had a large amount of fish, heavy feeding regime and also an environment where the elephants were kicking up a lot of dust.

Pond Spec and challenge

Zoo aquarium staff researched the market during visits to trade shows and eventually paid a visit to Evolution Aqua to see the Nexus in action and to discuss requirements. It seemed the Nexus system offered everything to fulfill the requirements, particularly given by the fact that its design caters for the husbandry of large ornamental carp and the main species for the zoo’s new exhibit are very similar to Koi.

Holding 5,000 gallons of water, the pond has two bottom drains that gravity feed two Nexus Eazy 300’s. Sequence 12,000 pumps return the water to the pond via a uv and in-line heater. There are in excess of 50 fishes in the pond when you include all the algae grazing catishes. The main exhibit fishes are all Asian and include Arowana, Probarbus, Clown loaches and Torpedo barbs, which, with the exception of the Arowana, are all cyprinids. Cyprinid is the scientific name given to carps and minnows and, as such, these fishes are related to Koi and, therefore, have very similar requirements to Koi. In fact the very large Probarbus are so similar to Koi, even in appearance, there requirements are pretty much identicle. As you can imagine, water quality is paramount to these fish and as the pond is on public display with a large viewing window, excellent clarity is also required! One thing big fish need is a large amount of food!

Feeding and Fish The different species within the exhibit occupy different water levels and have varying modes of eating. Because of this there is a tendency to slightly overfeed the system to ensure the less competitive fishes get their chance to feed. With such large fishes as the Probabus there is a risk they will plow through all the food whilst the smaller species keep their distance. Aquarists find there is now a happy medium and all fishes get their fare share of food. It is essential that the filtration can handle this type of feeding regime and to date this system has maintained excellent water quality despite of it.

The feeding regime includes 1.5kgs a week fed at x kg every day .This is made up of 50% beef heart, 40% fish protein, 5% vegetable matter (minced lettuce) and 5% dry feed (cichlid pellets and flake). In addition there is a once per week bloodworm feed, which is around 0.15kg.

The largest fish are on average 40lbs and it is estimated they may have all grown about 25% in body length and weight in the last year since the pond was built. With such large fishes it is extremely difficult to catch them for the purpose of weighing and measuring them without causing undue stress. Colin puts the growth down to good water, good feed and heating the pond at 27 C. He also believes that good filtration is the key to a healthy pond and inhabitants. ‘’The Kaldnes moving bed is the key factor when it comes to the biological quality of the water. The fish never appear listless or affected by pollutants normally associated with a large body of fish in a relatively small volume of water.’’

Colin also said that aquarium staff are always very busy and maintenance of systems that are overloaded can be time inconveniently consuming. The Nexus maintenance is so user friendly that regular back-washings are carried out with the minimum of effort in a short space of time.

If anyone would like to visit Chester Zoo, please check out all details and maps on this link … www.chesterzoo.org